v0.6.0

What's Changed

• remove MANUAL, it's replaced by OPTIONAL by @nedbat in #145
• Add section on Best Practices on How to Access Files in Rules by @jag250 in #133
• Rename fail.txt to output.txt and output.txt to error.txt by @jag250 in #137
• Add fail.txt functionality to testing docs by @jag250 in #136
• CLI commands and sub-commands docs reference page by @jag250 in #138
• replace optional bool with an enum. changes the JSON output! by @nedbat in #142

Full Changelog: v0.5.1...v0.6.0